EP1578038A1 - Dispositif et procede de control de reseau optique en temps reel - Google Patents

Dispositif et procede de control de reseau optique en temps reel Download PDF

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Publication number
EP1578038A1
EP1578038A1 EP04447069A EP04447069A EP1578038A1 EP 1578038 A1 EP1578038 A1 EP 1578038A1 EP 04447069 A EP04447069 A EP 04447069A EP 04447069 A EP04447069 A EP 04447069A EP 1578038 A1 EP1578038 A1 EP 1578038A1
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EP
European Patent Office
Prior art keywords
monitoring
branch
waveform data
network
optical
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Withdrawn
Application number
EP04447069A
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German (de)
English (en)
Inventor
Kivilcim Yuksel
Samuel Dupont
Dominique Hamoir
Laurent Robette
Fabrice Foucart
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MULTITEL
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MULTITEL
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Priority to EP04447069A priority Critical patent/EP1578038A1/fr
Priority to EP05447058A priority patent/EP1578039A1/fr
Publication of EP1578038A1 publication Critical patent/EP1578038A1/fr
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
    • H04B10/2513—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to chromatic dispersion
    • H04B10/25137—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to chromatic dispersion using pulse shaping at the transmitter, e.g. pre-chirping or dispersion supported transmission [DST]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H04B10/071—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using a reflected signal, e.g. using optical time domain reflectometers [OTDR]

Definitions

  • the present invention is related to a device and to a method for real-time automatic monitoring of optical fibre paths in multibranch optical networks.
  • Quality of service is key to multibranch optical access networks, as on the one hand, in order to keep the cost low, there is in general no protection scheme and on the other hand a disruption in the service would disconnect a specific user (small business, building, residential area,%) from broadband access (internet, TV, services, and even telephone).
  • OTDR Optical Time Domain Reflectometer
  • OTDR In point-to-multipoint architectures however, OTDR suffers from the problem that the backscattered signals from each branch add up together, making the interpretation of the OTDR trace taken at the head of the PON ambiguous.
  • usage of a multiwavelength OTDR to observe the branches individually was proposed (see patent US 5285305 A), but this solution, whereby a specific monitoring wavelength is assigned to each branch, is quite expensive due to the high cost of the tuneable OTDR and wavelength-selective filters.
  • Another simple and effective way of monitoring is to introduce a reference reflection at the end of each branch and to detect the presence and qualitative height variations of reference reflection peaks to identify the faulty branch.
  • the requirement of having branches of different lengths prohibits it to be a practical solution for a real, installed network (see L. Wuilmart et al., 'A PC-based Method for the Localisation and Quantisation of Faults in Passive Tree-Structured Optical Networks Using OTDR Technique', Proc. IEEE LEOS'96, Boston, USA, November 1996, pp. 122-123).
  • Patent application EP-A-02370054 discloses a monitoring method to determine the faulty branch as well as the fault parameters (type, location, loss, return loss) using a standard OTDR, that also works in case the optical distribution network has branches of equal length.
  • a major limitation of the method is that, after detection of a fault, it cannot be applied in a continuous way to the following successive faults. If more than one fault occurs, the method cannot determine anymore all of the above-mentioned parameters.
  • control system of EP-A-02370054 is based on the use of an optical time domain reflectometry (OTDR) equipment and of variable reflectors, named Switchable Reflective Elements (SRE), located at the end of the branches.
  • SRE Switchable Reflective Elements
  • the OTDR transmits the light signal (monitoring signal) at a specific wavelength dedicated to the monitoring purposes (monitoring wavelength) and has the capability of receiving and measuring the backscattered light from the fibres in the network and backreflected light from the SREs.
  • the monitoring method comprises the steps of :
  • the present invention aims to provide a device for real-time automatic monitoring of optical fibre paths in multibranch optical networks, like tree-structured PON, thereby overcoming the limitations of the prior art solutions.
  • the invention aims to provide a method for monitoring a network, using said device.
  • Present invention relates to a monitoring device for an optical network comprising a main line being connected to the network's head end, such as an optical line termination, at one end and to at least two branches at the other end, whereby the at least two branches may have either the same or a different length.
  • the monitoring device comprises an optical monitoring termination (OMT) being in connection with the network head end.
  • OMT optical monitoring termination
  • the monitoring device further comprises at least one wavelength selective coupling device, such as a WDM coupler.
  • the monitoring signals are pulsed signals and preferably OTDR signals.
  • the OMT communicates control commands to the OMU directly with optical signals.
  • the control commands are advantageously coded with series of optical pulses.
  • the OMT communicates control commands to the OMU indirectly via the network head end and an optical network unit being in connection with the OMU.
  • each OMU has its own address.
  • the OMT further comprises a list of the addresses of all of the OMUs.
  • the OMT is further in connection with external processing means and/or an external storage device.
  • the processing and memory storing can in that case be performed remotely, for instance by a supervision computer or workstation, such as those in charge of controlling the network or even a wider-area network including the network under monitoring.
  • the OMT is also arranged for communication with a network supervision unit.
  • the invention also relates to a method for monitoring a multi-branch optical network comprising a main line being connected to the network's head end at one end and to at least two branches at the other end by means of a monitoring device as described above. It comprises the steps of
  • the first step is preceded by the step of taking one-by-one a reference waveform data of each of the at least two branches.
  • the optional step may be performed of preprocessing the current waveform data.
  • the reference waveform data is the most recent reference waveform data that was determined for said current branch.
  • the steps as described above are performed repeatedly for all branches. Preferably they are performed repeatedly for all branches until a fault indication occurs.
  • the step is performed of determining the fault and parameters related to it.
  • the step of taking a reference waveform data is repeated after determination of a fault.
  • info about the fault and its parameters is stored in the OMT. Alternatively it may be stored in any proper place in the network.
  • only a selection of branches are equipped with such an OMU, the other one(s) being equipped with a simplified, permanently reflective OMU.
  • the use of permanently reflective OMU is advantageous for the longest branch as it reduces the cost while not requiring any specific data treatment.
  • Fig. 1 represents a self-consistent monitoring system for a point-to-multipoint system according to the invention.
  • Fig. 2 represents an implementation of the optical monitoring unit block.
  • Fig. 3 represents Example 1 of the method according to the invention.
  • Fig. 4 represents Example 2 of the method according to the invention.
  • Fig. 5 represents Example 3 of the method according to the invention.
  • Fig. 6 represents a scheme from which the general formula for the real loss calculation is derived.
  • Present invention relates to a device and method for automatically monitoring a multibranch optical communication network.
  • SRE switchable reflective elements
  • Fig.1 shows a diagram of the self-consistent monitoring system implemented in an n-branch standard PON. Telecommunication equipments are also depicted.
  • a unique Optical Line Termination (OLT) is connected to several Optical Network Units (ONUs) by several associated branches (n branches).
  • OLT Optical Monitoring Termination
  • OMU Optical Monitoring Unit
  • the OMT is located in the head end. It does not only comprise equipment to handle all optical time domain reflectometry (OTDR) functionalities, but is also able to communicate with various parts of the network, such as with the Optical Monitoring Units to send switching commands for the SRE, or with the OLT to send data.
  • the OMT communicates with OMUs in order to command the OMUs directly through optical signals as monitoring wavelengths or any proper wavelengths, or indirectly by using its connection with OLT (solid arrow in Fig.l), through which the commands are sent to ONU and finally conveyed to the OMU through the alternative command line between them (dashed arrow in Fig.1).
  • the OMT is arranged for sending information and commands to (or receiving from) the network supervision unit.
  • the OMT may also be connected to external storage and processing units.
  • An Optical Monitoring Unit (OMU) is located at the end of a selection of branches in the tree structured PON, preferably at the end of each branch.
  • the OMU handles the communication with the OMT and switches the switchable reflective element (SRE) that is included in it.
  • SRE switchable reflective element
  • the self-consistent monitoring device further comprises a wavelength selective device, such as WDM (Wavelength Division Multiplexing) couplers (or multiplexers (mux) /demultiplexers (demux)).
  • WDM Widelength Division Multiplexing
  • a monitoring wavelength is dedicated to the operation of the monitoring device.
  • the monitoring wavelength is inside or outside the communication channels wavelength bands, for example 1625 nm.
  • FIG. 2 shows a possible scheme of the OMU that is connected to the WDM coupler.
  • the monitoring wavelength is combined with/extracted from the communication signal wavelength by the WDM coupler. This allows transparency of the self-consistent monitoring device towards the communication network.
  • each OMU has its own address (like PCs in a Local Area Network). These addresses therefore are used to control each OMU individually allowing one and only one SRE to be switched to its 'on' state at a time when needed.
  • the photodiode (on one branch of the couplerl) converts optical signals from the OMT into electrical signals. The electronic circuit after the photodiode could use them to command the 'on/off' state of the switch during a certain amount of time that could be coded after the address (for more flexibility).
  • coupler coupledler2, preferably a 3dB-coupler
  • an optical switch plugged in between the two branches of the second coupler (representing together the SRE).
  • Coupler1 may be a WDM coupler to accommodate the case where another laser is used for communication with OMU at a wavelength different from monitoring wavelength.
  • each OMU should have its own address.
  • the OMT should preferably know the address of the each OMU connected to it. This can be obtained in several ways.
  • One possible solution can be that when a new OMU is installed, a technician checks the already distributed addresses, then gives a new one to the OMU and updates the OMT with the new address of the newly installed OMU. This clearly is an easy but inflexible solution.
  • a (more complex and more expensive) alternative could be to use a "bidirectional" OMU able to transmit information. This requires a modification of the OMU to add a laser next to the photodiode (or any other modification that gives the same functionality, such as using the switch as a modulator).
  • An advantageous solution can be to use an installation OMU : when a new OMU is installed, a bidirectional OMU is used to get an address, the address is copied into a basic OMU and the basic OMU is installed in the network. The installed OMUs then are basic ones (low cost) and only one bidirectional OMU is needed at installation. Asking these addresses can also be done through ONU and OLT by using the command lines (solid and dashed arrows in Fig.1).
  • 'current branch' The branch in which the SRE is in its 'on' state is called 'current branch'.
  • Another command including the address of the next branch is sent for analysing another branch.
  • a measurement is taken for each branch, when the SRE of only one branch is in its 'on' state and all the other branches' SREs are in their 'off' state.
  • Several branches of different lengths could have their SREs in 'on' state at the same time. In this case 'current branch' could refer to this group of branches.
  • branches can be equipped with permanently reflective OMUs, in particular the longest one. Also some branches can be disregarded either by not making the expense of an OMU for these branches or by keeping their OMU in their 'off' state for a while (e.g. while fixing faults).
  • OMT introduces an optical pulse to the input of the mainline of the multi-branch optical network, so that at the splitting point it is fractioned into optical pulses that simultaneously propagate in all the branches. These optical pulses are backscattered in their respective branches and backreflected by the reflective elements located at the Optical Monitoring Units (OMU). Backscattered and backreflected lights are recombined at the splitting point and form the 'response light'. It is converted into a digital 'waveform data', which represents the intensity of response light versus distance as discrete data points.
  • OMT includes conversion means comprising at least: a photodetection device, an amplification system, analog-to-digital conversion and digital processing facilities.
  • a waveform data is composed of two main parts: data points representing the backscattered part of the light form the 'backscattering signature' and the data points representing the backreflected light coming from SREs make up the 'end reflection peak'.
  • the waveform data taken for the current branch is called 'current waveform data'.
  • the 'reference waveform data' is a waveform data taken before the current waveform data.
  • Reference waveform data are taken for the first time at PON installation.
  • the reflective element belonging to the N th branch is in its reflective state while all the others are in their absorbent state.
  • reference waveform data are updated. Doing so allows discrimination between new and previous faults. Periodic updates of reference waveform data as well as keeping a record of all previous reference waveform data can be provided optionally in order to deal with slow degradations in the network.
  • the databases are used. These databases store the list of all parameters (type, location, loss,..) related to all the faults detected in the network, as well as some other parameters related to the network, such as attenuation coefficients of the fibre, length of the branches, .. etc. and the record of the reference waveform data (at least those relative to the previous faults). The values of the end-reflection peak variations are stored in the databases as well. These databases are physically kept in the OMT or in any other proper location in the network such as in the network supervision unit and created during network installation.
  • each branch is characterised as a point-to-point link in terms of attenuation coefficient at the monitoring wavelength and of the connection and splice losses/reflections contained in the branch. These losses/reflections and their locations together with the other parameters like the fibre attenuation coefficients are stored as initial values in the databases.
  • Example 3 will show that simultaneously occurring faults can also be dealt with in the monitoring method according to the invention.
  • Example 1 a N-branch point-to-multipoint network is shown together with the graphs illustrating the different waveform traces taken for branch-Y during the monitoring process at different times.
  • Lsp represents the apparent loss value of the 1:N splitter.
  • branch-Y being the current branch in the monitoring process. This is done by comparing the current waveform data related to branch-Y (dotted line) with the reference waveform data of branch-Y (dashed-dotted line).
  • the real loss can be calculated from the apparent loss (Lapp) using the above-mentioned equation 1.
  • Example 2 that is in fact a continuation of Example 1, a third fault (fault3, dashed cross) has occurred.
  • Fig.4 shows that the apparent losses of fault2 before the occurrence of fault3 (L app1 and L app2 for case 1 and 2, respectively) at the position of the fault 2 are different from the apparent losses of fault2 after the occurrence of fault3 (L app1 (after) and L app2 (after) for case 1 and 2, respectively), moreover they are not affected in the same proportion.
  • Each new fault will affect the apparent values of all previous faults located after the new fault. Therefore it is necessary to perform the analysis of discriminating new faults from the point closer to the OMT towards the points near to the OMUs. After determining a new fault, it is necessary to calculate all new apparent losses for all the previous faults located after the newly determined fault.
  • Example 3 illustrates a scenario where two simultaneous faults are detected (see Fig.5).
  • branch-X and branch-Y two faulty branches as their end reflection peaks are changed.
  • FIG.6 shows the problem in a general form.
  • L11, L12, ..., LN1, ..., Lla, L2b, LNd, ... L1A, L2B, ..., LND all represent real losses calculated for previously occurred and detected faults in the network
  • a, b, c, d are integer numbers representing number of faults in each branch before and at location X km.
  • A, B, C, D are integer numbers representing total number of faults in each branch (i.e.
  • a major advantage of the monitoring system is that it can be installed on any optical network without adaptation (ONU, protocols, ...), as the system is potentially compatible with all PON and can be physically inserted as a plug-in (at ONU and OLT sites).

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Optical Communication System (AREA)
EP04447069A 2004-03-19 2004-03-19 Dispositif et procede de control de reseau optique en temps reel Withdrawn EP1578038A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP04447069A EP1578038A1 (fr) 2004-03-19 2004-03-19 Dispositif et procede de control de reseau optique en temps reel
EP05447058A EP1578039A1 (fr) 2004-03-19 2005-03-18 Dispositif et procédé de contrôle de réseau optique en temps réel

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EP04447069A EP1578038A1 (fr) 2004-03-19 2004-03-19 Dispositif et procede de control de reseau optique en temps reel

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Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100740637B1 (ko) 2006-01-24 2007-07-18 주식회사 뮤텍스 광케이블 선로 상태 분석장치
FR2896644A1 (fr) * 2006-06-15 2007-07-27 France Telecom Dispositif de surveillance d'un reseau optique par echometrie
EP1986351A1 (fr) * 2007-04-26 2008-10-29 Alcatel Lucent Réseau optique, unité de surveillance et procédé de surveillance
EP1986350A1 (fr) 2007-04-26 2008-10-29 Alcatel Lucent Unité de surveillance, réseau optique et procédé d'exploitation pour le réseau optique
WO2010076567A1 (fr) * 2008-12-31 2010-07-08 Tyco Electronics Raychem Bvba Mesure d'atténuation optique absolue unidirectionnelle par réflectomètre optique dans le domaine temporel (otdr)
CN101964682A (zh) * 2010-10-22 2011-02-02 华为技术有限公司 分布式光纤故障定位方法和系统
WO2011070404A1 (fr) * 2009-12-11 2011-06-16 Universidade De Aveiro Système optique et procédé pour la surveillance de la structure physique de réseaux optiques, se fondant sur un réflectomètre rodt avec capteurs distants
WO2013002692A1 (fr) * 2011-06-30 2013-01-03 Telefonaktiebolaget Lm Ericsson (Publ) Analyse de trace rdto dans des systèmes rop
CN103852824A (zh) * 2014-02-28 2014-06-11 桂林聚联科技有限公司 一种用于pon网络监测的光纤反射器
WO2016034457A1 (fr) * 2014-09-03 2016-03-10 British Telecommunications Public Limited Company Identification de défaillance de réseau optique
CN106323187A (zh) * 2015-07-03 2017-01-11 中铁西北科学研究院有限公司深圳南方分院 边坡无源监测预警系统
WO2017206685A1 (fr) * 2016-06-02 2017-12-07 中兴通讯股份有限公司 Procédé et appareil pour mettre à jour une base de données de santé d'un réflectomètre optique temporel
CN107979413A (zh) * 2018-01-16 2018-05-01 北京益安佳光电科技发展有限责任公司 Pon光通讯终端状态普查仪
CN111130636A (zh) * 2019-12-31 2020-05-08 华为技术有限公司 一种光分配装置和光通信检测系统以及光通信检测方法

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EP1098458A2 (fr) * 1999-11-08 2001-05-09 Fujitsu Limited Dispositif et procédé pour localisation de défaut d'une ligne de transmission

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L. WUILMART, V. MOEYAERT, D. DANIAUX, P. MÉGRET, M. BLONDEL: "A PC-based method for the localisation and quantization of faults in passive tree-structured optical networks using the OTDR technique", IEEE LASER AND ELECTRO-OPTICS SOCIETY 1996 ANNUAL MEETING, vol. 2, 19 November 1996 (1996-11-19), pages 122 - 123, XP009035674, ISBN: 0-7803-3160-5 *

Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100740637B1 (ko) 2006-01-24 2007-07-18 주식회사 뮤텍스 광케이블 선로 상태 분석장치
FR2896644A1 (fr) * 2006-06-15 2007-07-27 France Telecom Dispositif de surveillance d'un reseau optique par echometrie
CN101296038B (zh) * 2007-04-26 2011-10-05 阿尔卡特朗讯 光网络、监控单元和监控方法
EP1986351A1 (fr) * 2007-04-26 2008-10-29 Alcatel Lucent Réseau optique, unité de surveillance et procédé de surveillance
EP1986350A1 (fr) 2007-04-26 2008-10-29 Alcatel Lucent Unité de surveillance, réseau optique et procédé d'exploitation pour le réseau optique
WO2008132118A1 (fr) * 2007-04-26 2008-11-06 Alcatel Lucent Réseau optique, unité de surveillance et procédé de surveillance
US8452173B2 (en) 2007-04-26 2013-05-28 Alcatel Lucent Optical network, monitoring unit and monitoring method
WO2010076567A1 (fr) * 2008-12-31 2010-07-08 Tyco Electronics Raychem Bvba Mesure d'atténuation optique absolue unidirectionnelle par réflectomètre optique dans le domaine temporel (otdr)
US9419707B2 (en) 2008-12-31 2016-08-16 CommScope Connectivity Belgium BVBA Unidirectional absolute optical attenuation measurement with OTDR
WO2011070404A1 (fr) * 2009-12-11 2011-06-16 Universidade De Aveiro Système optique et procédé pour la surveillance de la structure physique de réseaux optiques, se fondant sur un réflectomètre rodt avec capteurs distants
CN101964682A (zh) * 2010-10-22 2011-02-02 华为技术有限公司 分布式光纤故障定位方法和系统
WO2013002692A1 (fr) * 2011-06-30 2013-01-03 Telefonaktiebolaget Lm Ericsson (Publ) Analyse de trace rdto dans des systèmes rop
US9281892B2 (en) 2011-06-30 2016-03-08 Telefonaktiebolaget Lm Ericsson (Publ) OTDR trace analysis in PON systems
CN103852824B (zh) * 2014-02-28 2016-04-13 桂林聚联科技有限公司 一种用于pon网络监测的光纤反射器
CN103852824A (zh) * 2014-02-28 2014-06-11 桂林聚联科技有限公司 一种用于pon网络监测的光纤反射器
WO2016034457A1 (fr) * 2014-09-03 2016-03-10 British Telecommunications Public Limited Company Identification de défaillance de réseau optique
US10693555B2 (en) 2014-09-03 2020-06-23 British Telecommunications Public Limited Company Optical network faulted identification
CN106323187A (zh) * 2015-07-03 2017-01-11 中铁西北科学研究院有限公司深圳南方分院 边坡无源监测预警系统
WO2017206685A1 (fr) * 2016-06-02 2017-12-07 中兴通讯股份有限公司 Procédé et appareil pour mettre à jour une base de données de santé d'un réflectomètre optique temporel
CN107979413A (zh) * 2018-01-16 2018-05-01 北京益安佳光电科技发展有限责任公司 Pon光通讯终端状态普查仪
CN107979413B (zh) * 2018-01-16 2023-08-15 北京益安佳光电科技发展有限责任公司 Pon光通讯终端状态普查仪
CN111130636A (zh) * 2019-12-31 2020-05-08 华为技术有限公司 一种光分配装置和光通信检测系统以及光通信检测方法
CN111130636B (zh) * 2019-12-31 2021-08-13 华为技术有限公司 一种光分配装置和光通信检测系统以及光通信检测方法

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